CHAPTER V 



The vapor- 



capacity of 

 air. 



RAIN AND SNOW 



IN order to understand the phenomena of 

 rain and snow we mnst consider for a mo- 

 ment some facts established by the weather 

 men. I have no notion of trenching upon the 

 domain of the meteorologist. Indeed, I had 

 thought to write a book that would suggest 

 some of nature's beauties rather than its bare 

 facts, but I find it continually necessary to ex- 

 plain beauty by first showing structural char- 

 acter. 



The capacity of air for receiving and holding 

 vapor depends upon temperature. It is small 

 at low temperatures ; it is large at high tem- 

 peratures. That is to say, the vapor-carrying 

 capacity of a cubic foot of air is ten times as 

 large at 100 Fahrenheit as at 32. At either 

 temperature, when the cubic foot has all the 

 vapor it can carry, it is called "saturated." 

 When more vapor is crowded in than the cubic 

 foot can carry the result is condensation of the 

 surplus into cloud and rain. Perhaps this can 



